The invention relates to a continuous method for carrying out a multiphase aldol condensation reaction to obtain mixed α,β-unsaturated aldehydes by reacting a mixture of two aliphatic aldehydes having different numbers of carbon atoms, i.e. 2 to 5, in the molecule in a vertical tubular reactor in a concurrent flow in the presence of an aqueous solution of a basically reacting compound. In said method, the aldehyde mixture is dispersed in the aqueous phase in the form of drops, and the aqueous solution of the basically reacting compound flows through the tubular reactor as a continuous phase in laminar conditions.